Re: [Django] #14518: Field.to_python not called on foreign key IDs

[Django]

#14518: Field.to_python not called on foreign key IDs
-+-
 Reporter:  wolever  |Owner:  nobody
 Type:  Bug  |   Status:  closed
Component:  Database layer   |  Version:  master
  (models, ORM)  |   Resolution:
 Severity:  Normal   |  worksforme
 Keywords:   | Triage Stage:  Accepted
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Changes (by timgraham):

 * status:  new => closed
 * resolution:   => worksforme


Comment:

 I can't reproduce the behavior described in the ticket as far back as
 Django 1.2. `b.foo_id` and `b.foo.id` both return an integer. A look of
 the follow up comments use `SubfieldBase` which is deprecated in favor of
 `Field.from_db_value()`. If problems remain in newer versions of Django,
 please open a new ticket with details.

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Re: [Django] #14518: Field.to_python not called on foreign key IDs

[Django]

#14518: Field.to_python not called on foreign key IDs
-+-
 Reporter:  wolever  |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  master
  (models, ORM)  |   Resolution:
 Severity:  Normal   | Triage Stage:  Accepted
 Keywords:   |  Needs documentation:  0
Has patch:  0|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-

Comment (by timgraham):

 Yes, once we have a working patch and someone reviews it.

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Re: [Django] #14518: Field.to_python not called on foreign key IDs

[Django]

#14518: Field.to_python not called on foreign key IDs
-+-
 Reporter:  wolever  |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  master
  (models, ORM)  |   Resolution:
 Severity:  Normal   | Triage Stage:  Accepted
 Keywords:   |  Needs documentation:  0
Has patch:  0|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-

Comment (by antialiasis):

 Is there any chance this might be fixed in some way at some point?

 Like others, we've been using UUIDs as primary keys on a PostgreSQL
 database, and this bug is completely breaking `prefetch_related`. The way
 prefetching is implemented (at least in 1.7), instances are collected into
 a dictionary with their `to_python`'d primary keys as the keys, and then
 it tries to access them using the non-`to_python`'d foreign key ID field.
 Needless to say, this results in a KeyError if `to_python` changes the
 representation of the field at all (in our case, to strip PostgreSQL's
 native hyphens).

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Re: [Django] #14518: Field.to_python not called on foreign key IDs

[Django]

#14518: Field.to_python not called on foreign key IDs
-+-
 Reporter:  wolever  |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  master
  (models, ORM)  |   Resolution:
 Severity:  Normal   | Triage Stage:  Accepted
 Keywords:   |  Needs documentation:  0
Has patch:  0|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-

Comment (by slurms):

 @anubhav9042: looks like this is a problem with the way you're subclassing
 the `CharField`. When `to_python` is called, it could well already be in
 the right format, or it might be unset. `to_python` gets called every time
 the field is assigned a value and you are responsible for ensuring it is
 in the right format (https://docs.djangoproject.com/en/1.6/howto/custom-
 model-fields/#django.db.models.Field.to_python). Notice the two lines at
 the beginning of that example code. You will need to do something similar.

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Re: [Django] #14518: Field.to_python not called on foreign key IDs

[Django]

#14518: Field.to_python not called on foreign key IDs
-+-
 Reporter:  wolever  |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  master
  (models, ORM)  |   Resolution:
 Severity:  Normal   | Triage Stage:  Accepted
 Keywords:   |  Needs documentation:  0
Has patch:  0|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-

Comment (by anubhav9042):

 Thanks for your explanation. As I said my patch wasn't correct, it only
 was to tell which line caused errors.

 Now that I tried the following:
 {{{
 def to_python(self, value):
 return ".".join(value)
 }}}

 So the lookup which failed earlier passes, but as explained by Harm above,
 {{{
 >>> m2.foo_id
 u'a...n...u...b...h...a...v'
 >>> m2.foo.field
 u'a...n...u...b...h...a...v'
 }}}

 But it should have been: `u'a.n.u.b.h.a.v'`

 It seems that `to_python` is called too many times and that might be wrong
 when it is defined in a way like in my examples..

 Also if we remove `__metaclass__ = models.SubfieldBase` from our custom
 field then `to_python` does gets called but something strange happens as
 it appears it does not serves the purpose as always `u'anubhav'` is
 returned by `m1.field` or `m2.foo_id`.
 There might be problem in that metaclass implementation, but thats just a
 wild guess.

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Re: [Django] #14518: Field.to_python not called on foreign key IDs

[Django]

#14518: Field.to_python not called on foreign key IDs
-+-
 Reporter:  wolever  |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  master
  (models, ORM)  |   Resolution:
 Severity:  Normal   | Triage Stage:  Accepted
 Keywords:   |  Needs documentation:  0
Has patch:  0|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-

Comment (by Harm Geerts ):

 The reason the first example works is because in
 Bar.objects.create(foo=m1) the m1 Foo instance is cached on the Bar
 instance, so m2.foo.field does not perform a database query.

 The second example fails because m2 has to perform a database lookup, and
 that's where things get fun.

 Your MyField.to_python is called multiple times so the value stored in the
 database is actually "Value: Value: anubhavjoshi".
 When you access bar.foo the primary key value "Value: Value: anubhavjoshi"
 is passed through to_python again and becomes "Value: Value: Value:
 anubhavjoshi" and that primary key does not exist.

 The reason your patch works is because you only had one Foo record in your
 dataset.
 If you had multiple Foo records your test would raise
 MultipleObjectsReturned.
 The only thing the patch does is disable related lookup filters which is
 not what you want ;)

 It may be an idea to add a note to the documentation about custom field
 classes.

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Re: [Django] #14518: Field.to_python not called on foreign key IDs

[Django]

#14518: Field.to_python not called on foreign key IDs
-+-
 Reporter:  wolever  |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  master
  (models, ORM)  |   Resolution:
 Severity:  Normal   | Triage Stage:  Accepted
 Keywords:   |  Needs documentation:  0
Has patch:  0|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-

Comment (by anubhav9042):

 This might cause other tests to fail but might give some insight as to why
 this problem occured.
 As queryset gets the correct value earlier on and is changed to empty qs
 after that condition.

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Re: [Django] #14518: Field.to_python not called on foreign key IDs

[Django]

#14518: Field.to_python not called on foreign key IDs
-+-
 Reporter:  wolever  |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  master
  (models, ORM)  |   Resolution:
 Severity:  Normal   | Triage Stage:  Accepted
 Keywords:   |  Needs documentation:  0
Has patch:  0|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-

Comment (by anubhav9042):

 I am attaching a diff to fix what remains.

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Re: [Django] #14518: Field.to_python not called on foreign key IDs

[Django]

#14518: Field.to_python not called on foreign key IDs
-+-
 Reporter:  wolever  |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  master
  (models, ORM)  |   Resolution:
 Severity:  Normal   | Triage Stage:  Accepted
 Keywords:   |  Needs documentation:  0
Has patch:  0|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-
Changes (by anubhav9042):

 * cc: anubhav9042@… (added)
 * version:  1.2 => master


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Re: [Django] #14518: Field.to_python not called on foreign key IDs

[Django]

#14518: Field.to_python not called on foreign key IDs
-+-
 Reporter:  wolever  |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  1.2
  (models, ORM)  |   Resolution:
 Severity:  Normal   | Triage Stage:  Accepted
 Keywords:   |  Needs documentation:  0
Has patch:  0|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-

Comment (by anubhav9042):

 Well there have been some changes in the code and some things have
 changed.
 Here is my models.py

 {{{
 from django.db import models


 class MyField(models.CharField):
 __metaclass__ = models.SubfieldBase

 def __init__(self, *args, **kwargs):
 super(MyField, self).__init__(*args, **kwargs)

 def to_python(self, value):
 return "Value: %s" % value


 class Foo(models.Model):
 field = MyField(max_length=30, primary_key=True)

 class Bar(models.Model):
 foo = models.ForeignKey(Foo)

 }}}

 In shell, I get correct values here:
 {{{
 >>> m1 = Foo.objects.create(field="anubhavjoshi")
 >>> m2 = Bar.objects.create(foo=m1)
 >>> m2.foo_id
 u'Value: Value: anubhavjoshi'
 >>> m2.foo.field
 u'Value: Value: anubhavjoshi'
 }}}

 But if I do:
 {{{
 >>> m1 = Foo.objects.create(field="anubhavjoshi")
 >>> m2 = Bar.objects.create(foo=m1)
 >>> m2 = Bar.objects.all()[0]
 >>> m2.foo_id
 u'Value: Value: anubhavjoshi'
 >>> m2.foo.field
 DoesNotExist: Foo matching query does not exist.
 >>> m2.foo
 DoesNotExist: Foo matching query does not exist.
 }}}

 Following traceback:
 {{{
 ---
 DoesNotExist  Traceback (most recent call
 last)
 C:\Users\Anubhav\DjangoDev\apps\ in
 ()
 > 1 m2.foo

 c:\users\anubhav\django\django\db\models\fields\related.pyc in
 __get__(self, instance, instance_type)
 562 qs = qs.filter(extra_filter, **params)
 563 # Assuming the database enforces foreign keys,
 this won't fail.

 --> 564 rel_obj = qs.get()
 565 if not self.field.rel.multiple:
 566 setattr(rel_obj,
 self.field.related.get_cache_name(), instance)

 c:\users\anubhav\django\django\db\models\query.pyc in get(self, *args,
 **kwargs)
 374 raise self.model.DoesNotExist(
 375 "%s matching query does not exist." %
 --> 376 self.model._meta.object_name)
 377 raise self.model.MultipleObjectsReturned(
 378 "get() returned more than one %s -- it returned %s!" %
 (
 }}}

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Re: [Django] #14518: Field.to_python not called on foreign key IDs

[Django]

#14518: Field.to_python not called on foreign key IDs
-+-
 Reporter:  wolever  |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  1.2
  (models, ORM)  |   Resolution:
 Severity:  Normal   | Triage Stage:  Accepted
 Keywords:   |  Needs documentation:  0
Has patch:  0|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-
Changes (by MarkusH):

 * cc: info@… (added)


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Re: [Django] #14518: Field.to_python not called on foreign key IDs

[Django]

#14518: Field.to_python not called on foreign key IDs
-+-
 Reporter:  wolever  |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  1.2
  (models, ORM)  |   Resolution:
 Severity:  Normal   | Triage Stage:  Accepted
 Keywords:   |  Needs documentation:  0
Has patch:  0|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-
Changes (by kitsunde):

 * cc: kitsunde@… (added)


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Re: [Django] #14518: Field.to_python not called on foreign key IDs

[Django]

#14518: Field.to_python not called on foreign key IDs
-+-
 Reporter:  wolever  |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  1.2
  (models, ORM)  |   Resolution:
 Severity:  Normal   | Triage Stage:  Accepted
 Keywords:   |  Needs documentation:  0
Has patch:  0|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-
Changes (by avnimahajan@…):

 * ui_ux:   => 0
 * easy:   => 0


Comment:

 I am also facing same problem. We have changed the default behavior of
 having primary keys. Throughout our code it has been replaced with custom
 UUIDFiled(given below). Till django 1.1 we were not facing any problem but
 while migrating to django1.3, I started facing problem during
 syncdb(duplicate key error while inserting in auth_permissions).
 Since there is change in "django/contrib/auth/management/__init__.py"
 create_permission code. Now it is referring to "content_type" which is a
 Foreign key. In my case its value is not being to_python'd. Thus it fails
 in comparison with a uuid.UUID type value (returned when referred as pk
 which is always to_python'd).

 Please update by when this bug will be solved?


 class UUIDField(models.Field):


 __metaclass__ = models.SubfieldBase
 empty_strings_allowed = False

 def __init__(self, *args, **kwargs):
 if kwargs.get('primary_key', False):
 kwargs['editable'] = False
 kwargs['db_index'] = True
 super(UUIDField, self).__init__(*args, **kwargs)

 def db_type(self, connection):
 return 'uuid'

 def get_internal_type(self):
 return 'UUIDField'

 def to_python(self, value):
 if (value is None) or isinstance(value, uuid.UUID):
 return value
 try:
 return uuid.UUID(value)
 except (AttributeError, TypeError, ValueError):
 return value

 def pre_save(self, obj, add):
 old_val = getattr(obj, self.attname)
 if (self.primary_key and add) and (old_val is None):
 value = uuid.uuid4()
 setattr(obj, self.attname, value)
 return value
 else:
 return old_val

 def get_db_prep_lookup(self, lookup_type, value,connection=None,
 prepared=False):
 if lookup_type == 'exact':
 return [self.get_db_prep_value(value,connection=None,
 prepared=False)]
 elif lookup_type == 'in':
 return [self.get_db_prep_value(v,connection=None,
 prepared=False) for v in value]
 elif lookup_type == 'isnull':
 return []
 raise TypeError(u"Field has invalid lookup type: %s" %
 lookup_type)

 def value_to_string(self, obj):
 value = getattr(obj, self.attname)
 if value is None:
 return value
 else:
 return unicode(value)

 def formfield(self, **kwargs):
 defaults = {
 'form_class': forms.RegexField,
 'regex': UUID_REGEX,
 'max_length': 47,
 'error_messages': {'invalid': u"Enter only valid UUID."}
 }
 defaults.update(kwargs)
 return super(UUIDField, self).formfield(**defaults)

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Re: [Django] #14518: Field.to_python not called on foreign key IDs

[Django]

#14518: Field.to_python not called on foreign key IDs
+---
   Reporter:  wolever   | Owner:  nobody
 Status:  new   | Milestone:
  Component:  Database layer (models, ORM)  |   Version:  1.2   
 Resolution:|  Keywords:
   Triage Stage:  Accepted  | Has patch:  0 
Needs documentation:  0 |   Needs tests:  0 
Patch needs improvement:  0 |  
+---
Changes (by wolever):

 * cc: wolever (added)


Comment:

 It may also be worth noting: I have a StackOverflow question asking the
 same thing here: http://stackoverflow.com/questions/3983510

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Re: [Django] #14518: Field.to_python not called on foreign key IDs

[Django]

#14518: Field.to_python not called on foreign key IDs
---+
  Reporter:  wolever   | Owner:  nobody
Status:  new   | Milestone:
 Component:  Database layer (models, ORM)  |   Version:  1.2   
Resolution:|  Keywords:
 Stage:  Accepted  | Has_patch:  0 
Needs_docs:  0 |   Needs_tests:  0 
Needs_better_patch:  0 |  
---+
Changes (by russellm):

  * needs_better_patch:  => 0
  * stage:  Unreviewed => Accepted
  * component:  Uncategorized => Database layer (models, ORM)
  * needs_tests:  => 0
  * needs_docs:  => 0

Comment:

 Accepting, because it's clearly an inconsistency.

 However, I have a sneaking suspicion that this won't be easy to fix
 without breaking backwards compatibility. For historical reasons, it's
 possible to instantiate an object with string values, and those values
 aren't converted into field-appropriate values (integers, etc) until the
 object is saved to the database. This is an artefact of early-days Django
 form processing.

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[Django] #14518: Field.to_python not called on foreign key IDs

[Django]

#14518: Field.to_python not called on foreign key IDs
---+
 Reporter:  wolever|   Owner:  nobody
   Status:  new|   Milestone:
Component:  Uncategorized  | Version:  1.2   
 Keywords: |   Stage:  Unreviewed
Has_patch:  0  |  
---+
 Given a subclass of Field like this:

 {{{
 class MyIDField(Field):
 ...
 def to_python(self, value):
 return to_base_36(value)
 }}}

 Used like this:

 {{{
 class Foo(m.Model):
 id = MyIDField(primary_key=True)

 class Bar(m.Model):
 foo = m.ForeignKey(Foo)
 }}}

 Then the `MyIDField.to_python` function isn't called when `Bar.foo_id` is
 accessed:

 {{{
 >>> b = Bar.objects.all()[0]
 >>> b.foo_id
 1234
 >>> b.foo.id
 'ya'
 >>>
 }}}

 This is annoying for a few reasons, but most significantly because it
 breaks dropdown menus in admin: even if a value is set for a foreign key,
 the menu selects the default item (usually `--`). This is because the
 menu items *have* been `to_python`'d, but the default value has *not* been
 `to_python`'d).

 I'm seeing this in Django 1.2.1.

 If this is confirmed as a bug, I can submit test cases.

-- 
Ticket URL: 
Django 
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